ATM (Asynchronous Transfer Mode) switches are being employed as the switch fabric in telecommunications switches. In particular ATM switches are being used for inter-switch connections and to interconnect access gateways, e.g., line access gateways and trunk access gateways. These ATM services are being used for data and voice connections.
Several existing voice capabilities require moving a voice connection once it is established. For example, transferring a call or creating a conference call. Currently there is no capability for moving one end of an ATM communication. In order to provide traditional voice connections and features over ATM facilities, a procedure for movement of an ATM connection must be supported. One proposal for transfer or movement of a voice connection over ATM facilities is accomplished by using an inter-telephony switch signaling protocol to convey to the call control entities (telephone switches) that are connected to the voice connections the request for a transfer. The call control entities then instruct the access gateways to establish new ATM connections using ATM bearer signaling in accordance with the transfer. After the new connections are established, all the old connections are released. FIG. 1 and FIG. 2, which are discussed below, illustrate the problem and the proposed solution, respectively.
FIG. 1 is a block diagram of a communication system 100, including media access gateways (MAGs) 102, call control entities (CCEs) 104, and an ATM core 106. Media access gateways 102 are connected to the ATM core 106 via ATM facilities 109. The media access gateways 102 provide communication access for terminals, such as telephones 116,118 and 120. The ATM core 106 includes a plurality of ATM switches that are interconnected via ATM facilities 109. An exemplary arrangement for ATM core 106 shown in FIG. 1 includes ATM switch one 108, ATM switch two 110, ATM switch three 112, and ATM switch four 114. The number and arrangement of ATM switches varies. Call control entities 104 control the actions of the associated media access gateways 102. In addition, the call control entities 104 are coupled to an inter-telephony switch connection network, Signaling System 7 network 122, which provides the transport for bearer independent call control (BICC) signaling.
As shown schematically in FIG. 1, telephone 120 has a call path 124 established with telephone 116. Call path 124 traverses media access gateways 102 coupled to telephones 116 and 120, plural ATM facilities 109 and ATM core 106. More specifically, call path 124 includes a first segment 124a, a second segment 124b, a third segment 124c, and a fourth segment 124d. First segment 124a extends from media access gateway 102 over ATM facility 109 to ATM switch three 112. A switched connection 126a connects first segment 124a to second segment 124b at ATM switch three 112. Second segment 124b extends from ATM switch three 112 over ATM facility 109 to ATM switch two 110. A switched connection 126b connects second segment 124b to third segment 124c at ATM switch two 110. Third segment 124c extends from ATM switch two 110 over ATM facility 109 to ATM switch one 108. A switched connection 126c connects third segment 124c to fourth segment 124d. Fourth segment 124d extends over ATM facility 109 to media access gateway 102.
Another call path 128 traverses media access gateways 102 coupled to telephone 116 and 118, plural ATM facilities 109 and ATM core 106. More specifically, call path 128 includes a first segment 128a, a second segment 128b, a third segment 128c and a fourth segment 128d. First segment 128a extends from media access gateway 102 over ATM facility 109 to ATM switch four 114. A switched connection 130a couples first segment 128a to second segment 128b at ATM switch four 114. Second segment 128b extends from ATM switch four 114 over ATM facility 109 to ATM switch two 110. A switched connection 130b connects second segment 128b to third segment 128c at ATM switch two 110. Third segment 128c extends from ATM switch two 110 over ATM facility 109 to ATM switch one 108. A switched connection 130c couples third segment 128c with fourth segment 128b. Fourth segment 128d extends from ATM switch one 108 to media access gateway 102.
Call paths 124 and 128 are established in any suitable manner. Typically, call paths 124 and 128 are established using standards specified in ATM User-Network Interface (UNI) Signaling Specification, Version 4.0, af-sig-0061.0000 and ATM Forum Private Network-Network Interface (PNNI) Specification, Version 1.0, af-pnni-0055.00. After call paths 124 and 128 are established, a difficulty arises if one of the call paths is to be transferred or moved. For example, if telephone 116 desires to transfer call path 124 to call path 128 such that telephone 120 and telephone 118 are coupled together for voice communications, then a problem arises as to how the desired connections are to be established.
One known proposed solution for transferring call path 124 to call path 128 is illustrated in FIG. 2. In summary, a new connection is established between telephone 120 and telephone 118 and the old connections are released. More specifically, BICC signaling between call control entities 104 results in the call control entities 104 instructing the media access gateways 102 to establish the new ATM connection needed. The media access gateways 102 use UNI signaling to establish the new ATM connection. In particular, a new call path 140 is established to connect telephone 118 to telephone 120. Call path 140 traverses media access gateways 102 that are coupled to telephones 118 and 120, plural ATM facilities 109 and ATM core 106. More specifically, call path 140 includes a first segment 140a that extends from media access gateway 102 over ATM facility 109 to ATM switch four 114. A switched connection 142a couples first segment 140a to second segment 140b. Second segment 140b extends from ATM switch four 114 over ATM facility 109 to ATM switch two 110. A switched connection 142b connects second segment 140b to third segment 140c. Third segment 140c extends from ATM switch two 110 over ATM facility 109 to ATM switch three 112. A switched connection 142c couples third segment 140c to fourth segment 140d. Fourth segment 140d extends from ATM switch three 112 over ATM facility 109 to media access gateway 102. After establishing call path 140, call paths 124 and 128 are released.
One problem with the solution described above and illustrated in FIG. 2 is that the call control entity (switching node) needs to be aware of when another call control entity (switching node) in a call manipulates the call or bearer path. The bearer path, in effect, becomes a shared resource that all switching nodes jointly use to provide their own services. This greatly increases the complexity of implementing services where feature interactions cross switch boundaries. In light of this, a switching node is not able to perform call redirection and insert/remove service circuits in established connections to provide usual features (e.g., N-way bridging, announcement playback, tone generation, tone detection, speech recognition and multicasting) available to traditional time-division multiplexing (TDM) calls. Also, some resources are temporarily duplicated in order to establish the new connection. For example, portions of call path 124 and call path 128 replicate the new call path 140. The complexity required to establish the new connection using BICC signaling and the utilization of additional resources to establish the new connection makes this solution somewhat undesirable.
Therefore, a need exists for an improved transfer capability for ATM virtual channels.